From time to time you see a movie that stinks up the place, one that’s a special level of wretched that requires the cinema to be sprayed down with Febreze and sponged. Such is “King Arthur: Legend of the Sword,” a movie so awesome in its badness that it deserves special recognition.

The Warner Bros. film, from the studio that gave us “Batman v Superman,” has been in documented trouble for some time. Its opening was held back for months. Perhaps Warner hoped that giving the movie a long rest would break the fever that infected it with fast-cutting mania and computer-generated monsters. Or maybe they attempted some last-minute touch-ups to make it less overcrowded, noisy and frantic. Unfortunately, it is still relentlessly incoherent, more a gaudy, tacky, British-themed pinball machine than a carefully coordinated movie.

Writer/director Guy Ritchie (who did outstanding work in his debut films “Lock, Stock and Two Smoking Barrels” and “Snatch” and good-enough work in two Sherlock Holmes movies starring Robert Downey Jr.) is not interested in your grandfather’s story of classical chivalry in Camelot. Despite its 5th-century setting, this is a decidedly modern take on strangely enduring myths. Like many cases of amateur retrofitting, it’s better in the plan than the execution, never entirely figuring out what it wants to be. The problem isn’t the failure to examine Arthurian history and mythology, bypassing any real sense of history or development. It’s that the film aims low and misses the mark, anyway.

Charlie Hunnam, radiating minimal charisma, stars as Arthur, an orphaned urchin growing to manhood on the Cockney-style mean streets of ancient Londinium. There the much-abused boy learns self-defense from “Kung Fu George,” a wise Asian master because, of course, that’s how they did it back then.

By the time Arthur reaches adulthood, he is an affable, cocky player with many attractive wenches in the slummy brothel where he lives, just the type of lowlife scoundrel Ritchie used to populate his early, better films. He has only faded memories of witnessing his father, King Uther Pendragon (Eric Bana) dying at the hand of his triple-evil Uncle Vortigern (Jude Law, who sneers, grimaces and expects others to quiver in fear).

When fate draws Arthur into the rebel forces battling to knock Vortigern from the throne, his reaction is the less-than-noble announcement, “I’m not getting into this mess,” as required by the Joseph Campbell hero’s journey handbook of clichés. According to the bylaws, at least three refusals are necessary before an unexpected turn of heart is activated, and Ritchie follows the protocol to the letter. Would that he had paid equal attention to the film’s photography, which is as poorly lighted as a $100 million would-be blockbuster can be.

Hunnam’s character doesn’t develop so much as make abrupt leaps. A nameless magician (winsome Astrid Bergès-Frisbey from “Pirates of the Caribbean: On Stranger Tides”) sails him to a dark island inhabited by enormous bats and venomous snakes, triggering visions of his noble origin. When he touches the sword in the stone, Excalibur sends magical epiphanies through his system like a 50-amp generator. He learns the power of the sword in a climactic fight with Vortigern. It’s not so much a story line as a collection of exposition boxes to be checked.

The film seems to have been designed to appeal to the ever-more-important international market, where they like their action fantasies packed to the gills with gigantic mutant beasts and endless combat between characters that are never explored in more than a cursory way. There’s no shortage of that stuff in “King Arthur.” There are rats the size of mules, tentacled sea sirens from a “Little Mermaid” nightmare, attack elephants as big as Godzilla and a Goliath-style demonic antagonist wreaking havoc. As parkour chases and hand-to-hand combat erupt out of nowhere, people die of arrows, sabers and magical incineration effects.

Hectic as it is, the movie generates no sense of narrative or emotional momentum. Apparently intended as a franchise-starter, it feels more like an entire franchise shoved into one parcel and hurriedly wrapped with a roll of duct tape.

Proper bandaging would have served it better.